This invention relates generally to methods for making composite materials comprising nano-particulates and composite materials made thereby, and more particularly to methods for selectively placing nano-particulates on or within composites.
The use of advanced composites in various types of structures has been previously researched and it has been found that some composites have poor out-of-plane performance due substantially to matrix failure. Some textile composites also undesirably include matrix material-rich regions formed in gaps between interlaced fiber bundles of the textile composites. These matrix-rich regions, where cracks may initiate and propagate, are difficult to reinforce with traditional microscale fiber reinforcement.
Previously, the introduction of nano-particulates in advanced composites has been researched and heralded as a possible method for avoiding the aforementioned deficiencies. However, harnessing the benefits of these “multiscale” composites has been difficult due to inadequacies in current manufacturing methods. The majority of the reported work has been based on using sonication and shear techniques, including calendering, to disperse nano-particulates in liquid resins. The nano-particulate-doped resins then may be directly applied onto or infused into reinforcing fabrics to form composites. These techniques, however, are limited to doped resins that have about 3 weight % nanoparticles, as the doping of small amounts of nanoparticulates avoids an excessive rise in the resins' viscosities. Increased resin viscosity makes resin infusion difficult and inhibits fiber wetting. Other developments reported have involved growing nano-particulates on reinforcing fibers to form composites. Other research has demonstrated spraying nano-particulates directly on reinforcing or structural fibers prior to infusion of a resin to form composites.
It therefore would be desirable to provide improvements for introducing nano-particulates into composites. In particular, it would be desirable to provide cost-effective methods to selectively place dispersed nano-particulates wherever desired in composites while reducing or avoiding the aforementioned deficiencies. Improved nano-particulate composite materials would also be desirable.